By Keith Idec

The Adonis Stevenson-Badou Jack fight drew a peak audience of 611,000 viewers on Saturday night for Showtime.

According to ratings released Tuesday by Nielsen Media Research, the main event of a “Showtime Championship Boxing” doubleheader averaged 535,000 viewers. The Quebec-based Stevenson (29-1-1, 24 KOs) and Sweden’s Jack (22-1-3, 13 KOs) battled to a 12-round majority draw, which enabled the 40-year-old Stevenson to retain his WBC light heavyweight title at Air Canada Centre in Toronto.

Showtime’s viewership is based on subscribers in the United States. The Stevenson-Jack fight was televised via pay-per-view in Canada.

The live airing of the Stevenson-Jack fight began just before midnight on the East Coast. It was a highly competitive bout that resulted in two judges scoring it even (114-114) and a third judge scoring the fight for Jack by a slim margin, 115-113.

The opener of Showtime’s split-site doubleheader, Gary Russell Jr.’s victory over Joseph Diaz Jr. in a featherweight title fight, attracted a peak audience of 567,000 viewers. The average viewership for Russell-Diaz, which began around 10:30 p.m. ET, was 487,000.

Russell (29-1, 17 KOs), of Capitol Heights, Maryland, out-boxed the game Diaz to win a 12-round unanimous decision at MGM National Harbor in Oxon Hill, Maryland. Diaz (26-1, 14 KOs), of Downey, California, was the mandatory challenger for Russell’s WBC 126-pound championship.

The ratings for Saturday’s doubleheader were lower than for Showtime’s previous boxing broadcast, a tripleheader April 21 from Barclays Center in Brooklyn.

The main event of that three-bout broadcast, a 12-round majority draw between welterweights Adrien Broner (33-3-1, 24 KOs, 1 NC) and Jessie Vargas (28-2-1, 10 KOs), peaked at 891,000 viewers and averaged 782,000 viewers.

The opener of that telecast, in which Gervonta Davis (20-0, 19 KOs) knocked out Jesus Cuellar (28-3, 21 KOs) in the third round to win the WBA “super” 130-pound championship, was watched by a peak audience of 527,000 viewers and averaged 460,000. The second fight that night, in which Jermall Charlo (27-0, 21 KOs) knocked out Hugo Centeno Jr. (26-2, 14 KOs, 1 NC) in the second round to win the WBC interim middleweight title, peaked at 572,000 viewers and averaged 545,000.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.